On Fri, Aug 02, 2019 at 10:08:49AM +0100, Patrick Bellasi <patrick.bellasi@xxxxxxx> wrote: > @@ -7095,6 +7149,7 @@ static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf, > if (req.ret) > return req.ret; > > + mutex_lock(&uclamp_mutex); > rcu_read_lock(); > > tg = css_tg(of_css(of)); > @@ -7107,7 +7162,11 @@ static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf, > */ > tg->uclamp_pct[clamp_id] = req.percent; > > + /* Update effective clamps to track the most restrictive value */ > + cpu_util_update_eff(of_css(of)); > + > rcu_read_unlock(); > + mutex_unlock(&uclamp_mutex); Following my remarks to "[PATCH v13 1/6] sched/core: uclamp: Extend CPU's cgroup", I wonder if the rcu_read_lock() couldn't be moved right before cpu_util_update_eff(). And by extension rcu_read_(un)lock could be hidden into cpu_util_update_eff() closer to its actual need.
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